Problem: 8 rubber stamps cost $10.16. Which equation would help determine the cost of 4 rubber stamps?
Solution: There are several equations that could help determine the cost, each with a slightly different approach. We know the cost of 8 rubber stamps. We want to know the cost of 4 rubber stamps. We can write the numbers of rubber stamps as a proportion: $\dfrac{8}{4}$ We know 8 rubber stamps costs $10.16. We can let $x$ represent the unknown cost of 4 rubber stamps. The proportion of these costs can be expressed as: $\dfrac{\$10.16}{x}$ The cost changes along with the number of rubber stamps purchased, and so the two proportions are equivalent. $\dfrac{8}{4} = \dfrac{\$10.16}{x}$